Organic molecular crystals play an important role in a variety of industries, including that of molecular electronics and pharmaceutical production. While most crystals are rigid, co-crystals composed of caffeine and 4-chloro-nitrobenzoic acid (CNB) and those composed of caffeine and 4-bromo-3-nitrobenzoic acid (BNB) in methanol exhibit both elasticity and crystallinity, qualities that highlight the solvate as a promising instrument in pharmaceutical crystal engineering. In this study, we used computational methods to analyze the effects of methanol solvent concentration within a CAF-CNB cocrystal unit cell on thermodynamic free energy. Molecular dynamics simulations were used to calculate free energies for methanol concentration in the CAF-CNB co-crystal unit cell. In order to conduct molecular dynamic simulations on the CAF-BNB co-crystal, we parameterized the bromine atom using the Gaussian ‘09 suite of programs. We found that the free energy decreased for the CAF-CNB co-crystal as methanol concentration increased. Our molecular mechanics results for bromine after parametrization are similar to those calculated using quantum mechanics.

Importance of methanol absorption thermodynamics to the flexibility of caffeine: Halide-nitrobenzoic acid cocrystal

251st National Meeting (2016)

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